High pressure steam sterilization step - Huaqiang Electronic Network

Experimental principle

Autoclaving is to place the items to be sterilized in a closed pressurized sterilizing pot, and by heating, the water in the sterilizer is boiled to generate steam. Waiting for the steam to drastically drive the cold air in the pot out of the exhaust valve, then close the exhaust valve and continue heating. At this time, the steam can not overflow, and the pressure in the sterilizer is increased, so that the boiling point is increased. A temperature higher than 100 ° C is obtained. It causes the bacterial protein to coagulate and denature and achieve sterilization.
At the same temperature, the bactericidal effect of damp heat is greater than that of dry heat. There are three reasons for this: First, the bacterial cells in the damp heat absorb water, and the protein is easier to coagulate. As the water content of the protein increases, the required solidification temperature decreases (Table VI-2). Second, the penetration of damp heat is greater than that of dry heat (Table VI-3). Third, the hot and humid steam has latent heat. When 1 gram of water is at 100 ° C, it can release 2.26 kJ when it changes from gaseous to liquid. The heat of the coke). This latent heat can quickly increase the temperature of the object to be sterilized, thereby increasing the effectiveness of sterilization.
The general medium can be thoroughly sterilized by using 1.05kg/cm2 and 121.3°C for 15-30 minutes. The temperature of sterilization and the duration of maintenance vary depending on the specific conditions of the nature and capacity of the sterilized article. For example, the sugar-containing medium is sterilized at 0.56 kg/cm2 (8 psi) at 112.6 °C for 15 minutes, but in order to ensure the effect, the other ingredients can be sterilized at 121.3 ° C for 20 minutes, and then Sterile procedures are added to the sterilized sugar solution. Alternatively, the medium contained in the test tube may be sterilized at 1.05 kg/cm 2 and 121.3 ° C for 20 minutes, and the medium contained in the large bottle is preferably sterilized at 1.05 kg/cm 2 for 30 minutes. The unit of steam pressure is kg/cm2 (kg/cm2), and its conversion relationship with lb/in2 (pounds per square inch) and temperature is shown in Table VI-5.
The high-pressure steam sterilizers commonly used in the laboratory are vertical, horizontal and portable, and their structures are shown in Figure VI-4. This lab describes how to use a portable high pressure steam sterilizer.

Experimental reagent

Beef extract peptone medium

Laboratory equipment

Portable high pressure steam bacteria pot, etc.

Experimental Materials

Petri dish (6 sets of one pack)

Experimental procedure

1. First, remove the inner layer sterilization barrel, and then add an appropriate amount of water to the outer layer pot to make the water surface and the triangle shelf level. 2. Put back the sterilization bucket and load the items to be sterilized. Be careful not to pack too much, so as not to hinder the circulation of steam and affect the sterilization effect. Do not contact the barrel end of the flask and the end of the tube to prevent the condensate from drenching the paper at the mouth and penetrating into the tampon. 3. Cap and insert the exhaust hose of the cover into the exhaust groove of the inner sterilization tank. Then tighten the two bolts at the same time in a symmetrical manner to make the bolts tight and not leaking. 4. Heat with an electric stove or gas and open the exhaust valve at the same time to boil the water to remove the cold air from the pot. After the cold air is completely drained, close the exhaust valve so that the temperature inside the pot gradually increases as the steam pressure increases. When the pressure in the pot rises to the desired pressure, the heat source is controlled to maintain the pressure for the required time. This experiment was sterilized with 1.05 kg/cm 2 , 121.3 ° C for 20 minutes. 5. After the time required for sterilization, turn off the power or turn off the gas, let the temperature inside the sterilizer drop naturally. When the pressure of the pressure gauge drops to 0, open the vent valve, loosen the bolt, open the lid, and take out the sterilized items. If the pressure does not drop to 0, open the exhaust valve, the pressure in the pot will suddenly drop, so that the medium in the container will be flushed out of the flask mouth or the test tube mouth due to the imbalance of internal and external pressure, causing the cotton plug to contaminate the medium. Pollution. 6. The sterilized medium taken out was placed in a 37 ° C incubator for 24 hours, and it was checked if no bacteria were grown.

Precautions

Check that the medium is sterilized thoroughly.